1. Field of the Invention
The present invention is directed to a plunger conveyed plunger retrieving tool and a method of use. In particular, the present invention is directed to a plunger retrieving tool which is fabricated from existing components and may be conveyed and retrieved without use of wireline or other mechanisms.
2. Prior Art
Wells that produce natural gas also very often produce liquids such as oil or water. Natural gas and liquids flow into a wellbore due to the pressure inside the wellbore being less than the pressure in the surrounding reservoir. This differential pressure is sometimes referred to as “draw down”. If the flow rate of natural gas is high enough, the liquids are swept upwards and continuously removed from the wellbore by the velocity of the natural gas.
As the well ages, however, the flow rate of the natural gas will often decrease to the point where the velocity is insufficient to continuously remove the liquids from the wellbore. As the liquid “falls back”, a liquid level begins to form in the wellbore. This liquid level tends to exert a hydrostatic pressure. As the liquid level (and the hydrostatic pressure) increase, the pressure inside the wellbore at the formation face begins to increase. Since flow from the reservoir into the wellbore is governed by the differential pressure between the reservoir and the wellbore, any increase in pressure due to this liquid column reduces the flow from the reservoir into the wellbore. This is referred to as “liquid loading”. Once the hydrostatic pressure caused by the fluid column inside the wellbore is equal to the pressure in the reservoir, flow from the reservoir decreases to zero. The well is then described as being “loaded up”.
To alleviate this loaded up condition, various forms of artificial lift exists. Artificial lift is a broad term describing many methods that allow a well to be produced after natural flow has decreased. One such form of artificial lift is called “plunger lift”. Plunger lift is a form of artificial lift whereby the “plunger” is utilized to provide a solid interface between the natural gas and the liquid so as to prevent the liquid from falling back and accumulating in the reservoir. The plunger itself comes in various sizes and designs but includes a cylindrical metal object that has a diameter slightly smaller than the internal diameter of the wells production tubing. This close tolerance in diameters allows the plunger to move up and down the length of the tubing, but the tolerance is close enough that fluid that accumulates in the tubing is swept upward by the plunger. The plunger lift is a form of “intermittent” artificial lift so designated because the well is cycled through intermittent periods of being shut in and then opened up for production. These cycles are controlled automatically with valves and controllers typically supplied as part of the overall plunger lift installation.
The general operation of the plunger lift system is as follows:                1. A spring is installed in the bottom of a production tubing to cushion the fall of the plunger and prevent it from falling out the bottom of the tubing.        2. Surface equipment is installed on the well as follows:                    a. a “catcher” is installed on the wellhead to catch the plunger when it arrives at the surface.            b. a controller is installed that senses the arrival of the plunger and controls a valve on the flow line. This flow line valve is the mechanism by which the well is either shut in or opened to flow.                        3. Upon initial installation, the plunger is installed in the catcher and allowed to fall by gravity to the spring at the bottom. There is enough tolerance in diameters that the plunger will fall through fluid that has accumulated in the tubing.        4. The well is shut in at the surface using an automatic flow line valve. Pressure is then allowed to build on the well.        5. The surface controller can be programmed to open and close the flow line valve based on numerous parameters, such as time or pressure. Upon reaching a selected parameter, the flow line valve is opened. Since pressure is built on the well, flow occurs from the wellbore through the opened flow line valve. The plunger ascends from the bottom of the tubing, driven by the gas pressure below it. The plunger travels at a high velocity and its close tolerance allows minimal fluid to slip past the plunger as it travels up the tubing, pushing a column of fluid ahead of it. The fluid is removed from the tubing through the flow line as the plunger arrives at the surface.        
Flow is allowed until the controller senses a program parameter, such as time or pressure, at which time the controller signals the flow line valve to close and the well is shut in. The controller also releases the plunger from the catcher. The plunger falls to the spring on the bottom and the cycle is repeated.
During the course of the artificial lift operations, it is not unusual for the plunger to become stuck in the tubing. This may be caused by a number of factors. There may be a defect in the plunger or a failure in the tubing. Solids produced with the reservoir fluids, such as sand or salt, may cause the plunger to become stuck. It will be appreciated that the plunger may be stuck thousands of feet below the surface of the earth.
If the plunger becomes stuck at any time during the artificial lift operations, it may be necessary to employ a company or companies to perform a retrieving operation to retrieve the plunger. This is often described as a “fishing operation”.
In a traditional or conventional operation of retrieving or fishing a stuck plunger, a retrieving tool is installed by attaching to the end of a spooled wireline. The retrieving tool is then lowered into the tubing by gravity until it encounters the stuck plunger downhole. The retrieving tool attaches onto a fishing neck of the stuck plunger. The retrieving tool will latch onto the neck in a number of ways including grapples or flexible fingers. The wireline is thereafter pulled from the well with the stuck plunger engaged by the retrieving tool.
Typically, the wireline and specialized retrieving tools are not provided at each wellsite. Instead, various service companies provide this service as needed. The traditional means for retrieving or fishing stuck plunger results in expense for the wells' operator as the wireline operations are provided at a cost by various service companies.
Also in the past, attempts have been made to drop another object down into the well in an effort to dislodge the stuck plunger.
It would be desirable to fabricate a plunger retrieving tool from readily available components.
It would also be desirable to provide a plunger retrieving tool which operates without any wireline or similar mechanism.
It would also be desirable to provide a plunger retrieving tool and method of use that can be quickly and easily employed at a well site and then supplemented, if necessary, with traditional wireline fishing retrieval techniques.